In control systems such as switching power supplies, servo loops and robotic controllers, error detection precedes any other function within the control loop. Following error detection, the resultant error signals are shaped with a classical proportional-integral-derivative (PID) filter and fed to the controlling function for error correction. To achieve good performance under both transient and quiescent conditions, the entire signal path from error detection to the controlling function must have high resolution.
Digital rather than analog implementation of high-resolution loops offers many theoretical advantages, such as exceptional stability and programmability. In actual practice, however, digital loops never perform as well as analog loops due to circuit trade-offs in performance, size and power. On the other hand, eliminating large multipliers and adders in conventional approaches improves the cost-performance factor and thus allows digital loops to be superior to analog loops in that regard.
There is, therefore, a need in the art for cost-reducing circuit techniques in digital control loops that at least maintain the original resolution, or increase resolution while maintaining original circuit cost and power.